Table 1.

Colistin susceptibilities (mg/L) of the four selected resistant S. maltophilia strains determined by the BMD and Etest methods, and interpretation issues related to both methods.

Strain	BMD method		Etest method
	MICa	Transition zone in BMDb (concentration range)	MICc	Isolated colonies inside the inhibition halo (concentration range)
K279a	16	Yes (2–32)	4	Yes (0.125–4)
M30	32	Yes (8–128)	48	Yes (0.125–48)
D457	32	Yes (16–>256)	128	Yes (1.5–128)
PG157	32	Yes (8–64)	0.5	Yes (0.125–0.5)

^aMIC was defined as the lowest antibiotic concentration that inhibited 80% of growth (based on OD measurements) in the BMD plate. ^bWells in the BMD plate displaying incomplete growth inhibition and thus resulting in an ambiguous purple/pink color when stained with resazurin. ^cWhen small colonies grew within the zone of inhibition, the highest MIC intersect was recorded.